nowitech final event 22-23 august 2017 hvdc system and laboratory analysis … · 2017-08-25 ·...
TRANSCRIPT
HVDC system and laboratory analysisRaymundo E. Torres-Olguin, Research scientist [email protected]
NOWITECH final event 22-23 August 2017
Content
• Introduction• HVDC• Multiterminal HVDC• How to study a M-HVDC?• Power testbed• HIL approach• MMC technology • Final remarks
Introduction• In the late 19th century, Thomas Edison and Nikola Tesla were involved in a "battle"
now known as the War of the Currents.
Picture from http://revolve.media/the-great-war-of-the-current/
• During the early years of electricity, DC transmission was the standard.
• Today, the transmission is predominantly AC. The main reason is that AC current is easily converted to higher or lower levels.
• However, the transmission of large amounts of energy over long distance is more convenient in DC
HVDC
AC/DC converter AC/DC converterAdvantages:• Overall power losses are lower
in DC than AC for long distances.
• Shunt reactive compensation is not needed in HVDC
• AC/DC converters play an essential role in DC transmission.
• Converters provide full power flow control
Image: alstom
• A multi-terminal HVDC (MTDC) system consists of more than two converters connected through a DC network.
• Such a system can facilitate the large-scale integration of renewable energy and improve the power market.
• MT-HVDC systems have many components and complex control interactions.
• Extensive interoperability testing is essential to ensure safe and reliable operation under the wide range of possible operating conditions.
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Multiterminal HVDC (MT-HVDC)
From http://www.friendsofthesupergrid.eu/
How to study a MT-HVDC? • Testing on full scale systems is not
really feasible.
• Simulation models give a full test coverage with a limited test fidelity.
• Power testbeds have a good fidelity but limited test coverage. They are a bit expensive and not very flexible
• Hardware power-in-the-loop (HIL) simulation offers a good balance between test coverage and fidelity.
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Power testbed A scaled experimental platform was developed in SINTEF Energy Research with the following: Four 60 kVA VSCs The wind farm is emulated using a 55 kVA
induction motor/generator-set. The strong grids are represented by the
laboratory 400 V supply. An independent grid is emulated using a 17
kVA synchronous generator. The DC line emulator consists of variable
series resistors to vary the length of the emulated cable.
Parameter MTDC system Lab set up Scale factorPower 1200 MVA 60 kVA 1:20000DC voltage ±320 kV 640 V 1:1000AC voltage 400 kV 400 V 1:1000
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Smart Grid Laboratory at SINTEF and NTNU
Synchronous generator
Wind emulator
DC line emulator
4 VSC
Power testbed
Disconnection of two terminals using a decentralised droop control. System response is stable and with no overshoot against these severe events
Power testbed and some experimental results
Details in Experimental verification of a voltage droop control for grid integration of offshore wind farms using multi-terminal HVDC. Energy procedia 2014.
HIL approach
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MMC1860 kVA
MMC1260 kVA
2L VSC60 kVA
Main grid
Grid Emulator200 kVA
400 V ac
400V ac
700 V dc
Real Time Simulator
SINTEF Energy Research has three different MMCs
200 kVA High-Bandwidth Grid Emulator
Real time wind farm model
MMC technology
• MMC is emerging topology for offshore wind substations due to its black start capabilities, low Total Harmonic Distortion (THD) and high efficiency.
• The MMC uses a stack of identical modules.
• Each module create one level. The multiple voltage steps make the MMC being capable of producing very small harmonic content in the output voltage .
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LAP
APn
AP2
LAN
AP1
AN1
AN2
ANn
LBP
BPn
BP2
LBN
BP1
BN1
BN2
BNn
LCP
CPn
CP2
LCN
CP1
CN1
CN2
CNn
AC
DCP
N
ABC
C C
MMC technology
• MMC is emerging topology for offshore wind substations due to its black start capabilities, low Total Harmonic Distortion (THD) and high efficiency.
• The MMC uses a stack of identical modules.
• Each module create one level. The multiple voltage steps make the MMC being capable of producing very small harmonic content in the output voltage .
11
LAP
APn
AP2
LAN
AP1
AN1
AN2
ANn
LBP
BPn
BP2
LBN
BP1
BN1
BN2
BNn
LCP
CPn
CP2
LCN
CP1
CN1
CN2
CNn
AC
DCP
N
ABC
MMC technology
SINTEF Energy Research has designed and built three different MMCs:
• MMC unit with half bridge cells with 18 cells per arm
• MMC unit with full bridge cells with 12 cells per arm
• MMC unit with half bridge cells with 6 cells per arm
MMC technology
The power cell unitModules
Arm Main components in the MMCs:
MMC technology
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• 42 modules
• 144 power cellboards
• 1764 capacitors
MMC Assembling stages Some facts of the MMCs:
MMC technology
15
Ch1: Arm current, Ch2, Ch3: Arm voltages, Ch4: Phase current.
Figure shows a test of 18 level halfbridge converter
• Open loop, no current control• 100% modulation • Single phase RL load
Waveforms equal to simulations
Three MMC were commissioned on June 2017
Wind Farm Emulator
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Power Hardware in the Loop implementation combining the real time simulator and the grid emulator
• Flexibility in the model simulated
• Possibility to reproduce faster dynamics
IA
IB
IC
IA*
IB*
IC*
UA
UB
UC
Real Time Wind Farm Model UA*
UB*
UC*
Grid EmulatorReal Time Simulator
Current References
Voltage Measurements
Final Remarks
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• For long-distance bulk-power delivery, HVDC transmission is more attractive than HVAC transmission.
• MT-HVDC systems have many components, and complex control interactions. Testing on full scale systems is not really feasible in M-HVDC.
• Simulation models gives a full test coverage with a limited test fidelity.
• Power testbeds have a good fidelity but they are expensive and very little flexible.
• Hardware power-in-the-loop simulation offers a good balance between between low testbed cost, good test fidelity, and excellent test coverage.
Thanks
18
Picture by John Olav Tande
Thanks to all the sponsors